A box of a truck, such as a pickup truck, is illustrated in FIG. 1. This box conventionally includes a horizontally enlarged floor or bed assembly 12 which extends sidewardly between and is joined to generally parallel and upwardly extending side panels or walls 13. The side panels 13 conventionally have wheelwell housings 14 formed therein, the latter typically projecting at least inwardly a small extent into the interior of the box. The front end of the floor assembly 12 is also rigidly joined to an upwardly projecting front wall or panel 15, the latter extending between and being rigidly fixed to the side panels 13. The rear of the box is normally closed by a rear panel 16, the latter conventionally being an openable tailgate which is conventionally hingedly joined to the box and can swing into an open generally horizontal position wherein it is substantially flush with the floor assembly to provide access to the interior of the box.
This box, and specifically the floor or bed assembly 12, conventionally includes a horizontally enlarged main bed member 17, commonly referred to as the floor pan, which defines the actual floor of the box and extends lengthwise between the front and rear ends of the box, and has a width which normally substantially spans the width of the opening between the wheelwell housings. This main floor pan 17 is supported on a front cross rail 18, several intermediate cross rails 19, and a rear cross rail or sill member 21, the latter all extending transversely under the pan and being fixedly secured thereto, such as by spot welding. Some of these cross members, such as the front rail 18, the frontmost intermediate rail 19 and the rear sill 21 are typically fixedly secured to the vehicle frame (not shown) in a conventional manner.
The bed assembly 12 also normally includes secondary bed or floor pan members 22, the latter being positioned adjacent and fixedly joined to opposite longitudinal edges of the main floor pan 17 so as to occupy the regions of the bed disposed forwardly and rearwardly of the wheelwell housings 14.
In the pickup box as conventionally constructed, the main floor pan 17 is provided with stiffening ribs 23 which project upwardly from the pan, with a plurality of such ribs being generally uniformly sidewardly spaced apart across the width of the pan and extending longitudinally of the pan over a majority of the length thereof. These ribs, which are deformed upwardly from the pan to define a downwardly-opening channel-like cross section, generally extend rearwardly from the front free edge of the main pan 17 but the ribs normally terminate in tapered rib ends 24 which merge downwardly into the planar profile of the pan 17 at a location disposed close to but spaced forwardly a small distance from the rear free edge 25 of the pan. The rear edge portion of the main pan 17, namely the flat portion thereof which is free of the ribs, is then normally seated within a shallow recess formed in the topwall of the rear sill member 21 so as to be substantially flush with the upper surface of the sill member, with the rear pan and sill member then being suitably fixedly secured together, such as by spot welding. This arrangement enables the groove-like regions defined between adjacent ribs 23 to freely open outwardly through the rear end of the bed assembly, and hence prevent creation of pockets or recesses which would collect dirt or moisture.
A bed assembly having the structure described above has, for a very long time, been constructed using individual members which have been stamped utilizing large forming presses. That is, the main floor pan 17 as well as the cross rails 18, 19 and 21 have been conventionally formed from flat steel sheets by positioning a precut steel sheet in a forming press which deforms the sheet to define the desired cross section of the finished member. This stamping or press-forming technique, even though extensively utilized for many years, and which in fact is still in use, possesses recognized disadvantages which have nevertheless been long tolerated in view of the belief that this was the best manner of constructing the bed assembly.
More specifically, and particularly with respect to the main floor pan 17, the current and almost universally utilized technique of stamping the pan has resulted in limitations which have restricted optimum construction of the pan. For example, to stamp the main floor pan 17, a large rectangular sheet must be precut in accordance with the size of the desired pan being stamped. The sheet is initially of excess width so as to provide portions along opposite edges of the sheet which can be used for clamping the sheet and holding it in position when the sheet is positioned within the press and subjected to the stamping operation. Further, during the actual stamping operation, the material of the sheet is physically deformed by the stamping die so as to permit creation of the longitudinal ribs. This necessarily results in significant changes in thickness of the sheet material due to the deformation which is caused during the rib formation process. Not only does the sheet undergo significant changes in thickness, but this change in thickness is also of varying amounts at different locations across the rib, or through the cross section of the sheet containing the ribs, so that the resulting stamped floor pan has a sheet thickness which has significant variation therein. This thickness variation can in some instances be as much as 40% to 50%. This stamping process has also been observed to result in bends or corners which are inconsistent in terms of both material thickness and included angle, and have provided a finished exterior appearance which permits such irregularities to be visually observed. This stamping operation also requires, after the pan has been stamped, that the pan be subjected to a further stamping or cutting operation which is effective for removing the clamping strip portions on opposite sides of the sheet, which strip portions are disposed of as scrap.
In view of the inherent but inconsistent thickness reductions which occur during forming of the pan by the stamping or pressing process, the pan must also be initially formed from a sheet material of greater thickness than desired so as to compensate for the expected thickness reductions which occur during the stamping operation. This increases the overall weight of the pan. Further, in view of the significant size of the main floor pan and the fact that it is deformed or stamped in basically a single pressing operation, this also necessitates utilization of an extremely large and high-capacity forming press in order to accommodate both the size of the sheet and the significant pressing force encountered during the simultaneous deformation of the numerous ribs which extend longitudinally thereof. Further, these stamping operations necessarily can normally be successfully carried out only if lower strength and softer sheet steels are utilized since harder and higher strength steels will typically split or crack if subjected to severe deformation of the type encountered in the conventional pan stamping operation.
To improve on the above described truck bed structure and the forming method thereof, the assignee of this application developed the improved truck bed structures and forming methods as disclosed in U.S. Pat. No. 5,188,418, U.S. Pat. No. 5,544,932, and PCT published application WO 93/19972. All are assigned to Pullman Industries, the assignee hereof, and are herein incorporated by reference.
In said U.S. Pat. No. 5,188,418, a truck bed is disclosed including a floor pan having strengthening ribs constructed by a roll forming process. A rear sill member cooperates with the rear edge of the floor pan to close off the floor pan from the rear and substantially abut the rear free edge of the floor pan. The rear sill member has upward protrusions which interfit within and close off the rearward ends of the ribs formed in the pan. U.S. Pat. No. 5,544,932 relates to a variation wherein the rear sill is formed of two distinct elongate components, the first being welded on top of the second, with the first elongate component having rib-closing protrusions to close off the ribs on the floor pan.
In a continuing effort to improve truck beds, a truck bed manufactured substantially by roll forming techniques having a strengthened rear edge and rear part of the truck bed is desired to prevent damage to the truck bed. Thicker truck beds may be manufactured, however this increases the cost of the truck bed and makes it more difficult to efficiently form the truck bed. Further, the increased weight of a thicker truck bed decreases the efficiency of operation of a truck, i.e. gas mileage, suspension wear, tire wear, etc.
Accordingly, it is an object of this invention to provide an improved truck bed assembly and forming method which overcomes not only the disadvantages associated with the conventional and long-utilized stamped bed assembly as described above, but which is also believed to further improve upon the desirable truck bed structures and forming methods disclosed in the aforesaid patent and copending application.
More specifically, the present invention relates to an improved truck bed assembly wherein the floor pan has a flange on the rear edge thereof, which rear flange reinforces the rear edge of the floor pan where the floor pan is most susceptible to damage.
The present invention, in addition to the improvements and advantages briefly summarized above, is also believed to provide cost savings with respect to the overall manufacturing process, and permits creation of cross sections or shapes in the bed which are not possible with a stamping operation, including the creation of sharper corners having a higher consistency with respect to both curvature and thickness of bends.
Other objects and purposes of the invention will be apparent to persons familiar with structures and processes of this general type upon reading the following specification and inspecting the accompanying drawings.